Problem: There was a group of unicorns talking in a field. $7$ of them ran away. $9$ of them were left. In total, how many unicorns were talking in a field?
Answer: We can use subtraction to find the missing whole: ${\Box} - {7} = 9$ We can also add all of the unicorns together: ${7} + 9 = {\Box}$ ${16}$ unicorns